<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>position-relative</title>
    <style type="text/css">
        div div{
            border: 1px solid #f00;
            height: 100px;
            width: 160px;
            float: left;
        }
        #box-relative{
            position: relative;
            top: 20px;
            left: 10px;
        }
    </style>
</head>
<body>
<div>
<div>块1</div>
<div id="box-relative">块2</div>
<div>块3</div>
</div>
</body>
</html>